In television receivers, the advent of solid state integrated circuit electronic technology has permitted a substantial reduction in the space required within a cabinet for housing the electronic components. As a consequence, the cabinet size is primarily dictated by the size of the picture tube and the space required for the tuner, channel number display mechanism, and other control knobs and switches for operating the receiver. It is desirable to make the television receiver as compact and lightweight as possible, both to increase the portability of such receivers and also to decrease their weight and size. One of the limiting factors in design flexibility and in reducing the size of a television receiver cabinet, however, is the tuner and channel number display mechanism.
Since the programs displayed on television receivers are generally viewed from a substantial distance, such as 10 or 15 feet, it is necessary to display the channel number indicia as large as possible; so that it may be readily discerned from a viewing position across the room. Large channel number indicia, however, are somewhat incompatible with compact channel number display mechanisms. One method for displaying channel numbers is to imprint the channel numbers for the VHF channels and/or UHF channels on a translucent disc which is concentrically mounted on the channel number tuner selector shaft for rotation with the shaft. The numbers on the disc are then rotated to a window viewing position where they may be observed by the television set viewer. Generally, a suitable light source is placed behind the indicia disc to illuminate the numbers. Because of the distance involved, it is desirable to make the numbers fairly large, approximately 3/4 inch to 1 inch in height, and if they are placed on a disc of this type, it is apparent that a relatively large-diameter disc is required to accommodate all the different numbers. To overcome the problem of the large size inherent in such an approach, other techniques for displaying channel numbers have been used and proposed.
One solution is a combination of a channel number disc or drum of the type described above but in which the numbers are much smaller. These numbers are then projected through an optical magnifying lens system which projects the selected channel number to the viewer through a channel number indicator aperture in the cabinet. Such a system, however, results in an increased expense because of the optical system required. Another solution which has been proposed is to electronically decode either the rotational shaft position of the channel selector shaft or to use a digital channel selection and drive appropriate seven-segment illuminated digital displays to produce and display the selected channel number. This type of system, however, requires relatively expensive electronic circuitry and the associated electronic display segments to accomplish the channel number display.
Another system which has been proposed is to generate channel number indicia electronically and to couple this generated indicia signal into the video signal of the television receiver, either momentarily on command or each time a channel number is displayed; so that the channel number then is viewed directly on the picture tube screen of the television receiver. Once again, additional electronics is required to effect such a channel number display. A drawback of this latter type of system is that such displays are generally temporary; so that the viewer does not know what channel he is watching during the course of the program unless he effects an appropriate channel number display command. Alternatively, if such a channel number indicia display is permanently present in a small portion of the TV picture, it detracts from the video portion of the television program material which is being watched.
A mechanical alternative to the foregoing systems is to place the channel numbers on an endless belt or tape which is moved in accordance with the rotation of the channel selection knob of a mechanical tuner. The different detented positions of the channel selector knob then cause the movement of the channel number display belt or belts to be effected to display the proper indicia for the selected channel number in a display window in the television cabinet. Under some operating conditions, the plastic material which typically is used in such belts may become brittle and break. In addition, such endless belt-type display systems generally are found to exhibit a relatively high amount of mechanical friction. This is undesirable.
It is desirable to provide a turret indicator for indicating the channel numbers of selected channels in a television receiver, or for indicating rotational positions in other devices, which is capable of displaying large numerals or indicia for a large number of indicator positions in a relatively small space, with a relatively simple mechanical mechanism capable of being manufactured at low cost.